#include<cstdio>//uncle-lu
#include<algorithm>
template<class T>void read(T &x)
{
	x=0;int f=0;char ch=getchar();
	while(ch<'0'||ch>'9') { f|=(ch=='-'); ch=getchar(); }
	while(ch<='9'&&ch>='0') { x=(x<<1)+(x<<3)+(ch^48); ch=getchar(); }
	x = f ? -x : x;
	return ;
}

int n;
int map[1010][1010];
int F[1010][1010];//表示状态

int main()
{
	read(n);
	for (int i = 1; i <= n; i++) 
		for (int j = 1; j <= i; j++) 
			read(map[i][j]);

	//初始化状态
	for (int i = 1; i <= n; i++) 
		F[n][i] = map[n][i];

	//状态转移 // 决策
	for (int i = n-1; i >= 1; i--) 
		for (int j = 1; j <= i; j++) 
			F[i][j] = std::max(F[i+1][j], F[i+1][j+1]) + map[i][j];

	printf("%d", F[1][1]);

	return 0;
}
